The embodiments disclosed herein are directed to improvements in the tooling used in compaction equipment and tableting machines, for example, tooling used in the manufacture of components for dry-cell batteries, e.g., various sizes of 1.5 volt (AAA, AA, C, D) and 9 volt batteries used in consumer electronic devices. It will be further appreciated that various aspects of the invention described herein may be suitable for use with well-known compaction tooling and tableting equipment, and particularly to center pins and punches employed in the manufacture of oral pharmaceuticals, etc.
Heretofore, a number of patents have disclosed processes and apparatus for the forming of parts by the compression of unstructured powders, sometimes followed by heat-treating of the compressed part. The relevant portions of these patents may be briefly summarized as follows; and are hereby incorporated by reference for their teachings:
U.S. Pat. No. 5,036,581 of Ribordy et al, issued Aug. 6, 1991, discloses an apparatus and method for fabricating a consolidated assembly of cathode material in a dry cell battery casing. Ribordy further states that in certain types of galvanic dry cell batteries, such as the so-called alkaline type, the battery construction generally consists of a metallic casing or container (usually a suitable steel), an annular mass or mix of cathode material (e.g., a molded mixture of MnO2 and graphite) in the casing, a separator membrane (e.g., a paper liner) on the inside surface of the annular molded cathode mix, and an electrolyte as well as an anode material (e.g., a zinc powder) in the form of a central anode core within the separator membrane.
The casing is generally cylindrical, is closed on one end, and is initially open at the other end for receiving the internal components and materials. Good physical contact between the cathode mix and the casing is required so as to provide the proper electrical conduction which is critical to battery performance. Consequently, it would be desirable to provide an improved method and apparatus for the manufacture of a dry cell battery which would result in good physical contact between the cathode mix and the surrounding surfaces of the casing. Further, it would be beneficial if an improved method and apparatus could efficiently provide good contact between the casing and cathode material on a consistent basis in high speed production operations.
U.S. Pat. No. 5,122,319 of Watanabe et al, issued Jun. 16, 1992, discloses a method of forming a thin-walled elongated cylindrical compact for a magnet.
U.S. Pat. No. 4,690,791 of Edmiston, issued Sep. 1, 1987, discloses a process for forming ceramic parts in which a die cavity is filled with a powder material, the powder is consolidated with acoustic energy, and the powder is further compressed with a mechanical punch and die assembly.
U.S. Pat. No. 5,930,581 of Born et al, issued Jul. 27, 1999, discloses a process for preparing complex-shaped articles, comprising forming a first ceramic-metal part, forming a second part of another shape and material, and joining the two parts together.
Referring to FIG. 1, there is illustrated a prior art compaction tool as might be employed for the production of a cylindrically shaped battery component. In use of such a tool in battery manufacturing, the die 20 receives a lower punch 22 that is inserted into the die. The lower punch includes a through-hole in the center thereof that allows a center pin 24 to be inserted therein. The punch and center pin then, in conjunction with the die, form a cavity into which a powder mix employed in battery manufacture can be deposited. Such a powder mix may include wetting agents, lubricating agents, and other proprietary solvents added just before filing the die cavity. Once filled, the cavity is then closed by an upper punch 26 that is inserted into the upper end of the die and the punches are directed toward one another so as to compact the powder material 28 therein. In typical systems, the compaction force is applied by mechanical and/or hydraulic systems so as to compress the powder material and produce a compacted part (e.g., a tablet or a cylindrical component), examples of which are described in the patents incorporated by reference above.
During the compaction process, however, the application of significant compressive forces results in wear to the tips and heads of the punches. This force, associated friction and the nature of the materials being compacted, causes a high level of wear on the compaction tooling, resulting in the frequent need to change out and rework such tooling. Although it is known to employ ceramics in the interior region of the die, to reduce the wear from friction, replaceable or refurbishable tools such as compaction punches, possibly including ceramics have not been successfully employed.
Thus, it is often the case that frequent replacement of punches and center pins continues to be a problem and cost that plagues the powder compaction industry. One prior art method and apparatus for the manufacturing of cylindrical dry cell batteries, which entails the compression of powdered material is described in U.S. Pat. No. 5,036,581 of Ribordy et al., previously incorporated by reference.
The disclosed embodiments are, therefore, directed to both an apparatus that successfully facilitates refurbishment of the wear surfaces of compaction tooling such as punches, as well as the methods of making and refurbishing the same. In particular, the disclosed embodiments include alternatives for affixing a replacement tip component (or head on the opposite end of the punch) to the end of a metal punch; the selection of a particular alternative or method may be dependent upon the use characteristics for the apparatus.
In accordance with an aspect of the disclosed embodiments, there is provided a method of refurbishing a compaction punch, comprising: receiving the used compaction tool for repair; cutting off the worn end of the compaction tool (e.g., tip, head); grinding the remaining body of the compaction tool (e.g., punch), and optionally placing a chamfer or other profile on one or more mating or adjacent surfaces; aligning the punch to permit accurate placement of a replacement piece relative to the remaining body (e.g., insert alignment tool into hollow punch body); placing a replacement end (opt. also with chamfer) in alignment with the remaining body (e.g., position new tip on the alignment tool); clamping the replacement end (e.g., tip) to remaining body; permanently affixing replacement end to remaining body; unclamping and removal of alignment tool; and finish working (e.g., grind/polish) replacement portion of punch.
In accordance with another aspect of the disclosed embodiments, there is provided an assembly for refurbishing a compaction punch, including: a used body for a compaction tool, said body having a worn end removed therefrom; a replacement end to be permanently affixed to the body where the worn end was removed; and an alignment tool, operatively associated with the compaction tool to assure alignment of the replacement end and the body prior to and during the permanent affixing of the body and replacement end.
In accordance with yet another aspect of the disclosed embodiments, there is provided a refurbished compaction tool, comprising: a used body for a compaction tool having a worn end removed therefrom; and a replacement end permanently affixed to the body where the worn end was removed.
One aspect of the invention is based on the discovery of techniques for permanently affixing a replacement tip or surface for a punch that will survive the high compaction stresses of a compaction apparatus. The techniques described herein not only allow for the successful attachment of replacement tips, but also the reworking and replacement thereof, so that only damaged or worn components are replaced, and not the entire punch.
The techniques described herein are advantageous because they can be adapted to any of a number of compaction tooling applications. In addition, they can be used in other similar compaction embodiments to allow for the use and refurbishment of various materials, possibly including ceramic materials, in high-friction environments. An advantage of the disclosed embodiments and methods is reuse of a highly machined part, but only as necessary to replace/refurbish the portion that is worn. The techniques of the invention are advantageous because they provide a range of alternatives, each of which is useful in appropriate situations. As a result of the invention, the life of compaction tooling, particularly including punches, may be significantly increased and/or the cost of reworking and refurbishing the same may be reduced.
The present invention will be described in connection with a preferred embodiment, however, it will be understood that there is no intent to limit the invention to the embodiments and methods described herein. On the contrary, the intent is to cover all alternatives, modifications, and equivalents as may be included within the spirit and scope of the disclosure.